Solid/gas chemical heat pump installations are already known which make use of the phenomena of adsorption or absorption. Compression refrigerating machines are likewise known which also use ammonia as the refrigerant fluid. These machines have, however, a number of drawbacks such as the risks of serious accidents in the event of corrosion of the exchangers, when the ammonia is then released into the surroundings. The difficulties posed by the ammonia pressure reduction members in chemical refrigerating machines are also known. Moreover, indirect systems for producing cold generally require auxiliary pumps to transfer the fluids, and relatively complex regulating devices. Such installations are not however entirely satisfactory because they lead to higher costs, and entail additional energy consumption whilst making regulation complicated.